dnsmgr.c File Reference

Background DNS update manager. More...

#include "asterisk.h"
#include "asterisk/_private.h"
#include <regex.h>
#include <signal.h>
#include "asterisk/dnsmgr.h"
#include "asterisk/linkedlists.h"
#include "asterisk/utils.h"
#include "asterisk/config.h"
#include "asterisk/sched.h"
#include "asterisk/cli.h"
#include "asterisk/manager.h"
#include "asterisk/acl.h"

Include dependency graph for dnsmgr.c:

Go to the source code of this file.

Data Structures
struct	ast_dnsmgr_entry
struct	refresh_info
Defines
#define	REFRESH_DEFAULT   300
Functions
int	ast_dnsmgr_changed (struct ast_dnsmgr_entry *entry)
	Check is see if a dnsmgr entry has changed.
struct ast_dnsmgr_entry *	ast_dnsmgr_get (const char *name, struct sockaddr_in *result, const char *service)
	Allocate a new DNS manager entry.
int	ast_dnsmgr_lookup (const char *name, struct sockaddr_in *result, struct ast_dnsmgr_entry **dnsmgr, const char *service)
	Allocate and initialize a DNS manager entry.
int	ast_dnsmgr_refresh (struct ast_dnsmgr_entry *entry)
	Force a refresh of a dnsmgr entry.
void	ast_dnsmgr_release (struct ast_dnsmgr_entry *entry)
	Free a DNS manager entry.
	AST_MUTEX_DEFINE_STATIC (refresh_lock)
static	AST_RWLIST_HEAD_STATIC (entry_list, ast_dnsmgr_entry)
int	dnsmgr_init (void)
static int	dnsmgr_refresh (struct ast_dnsmgr_entry *entry, int verbose)
int	dnsmgr_reload (void)
void	dnsmgr_start_refresh (void)
static void *	do_refresh (void *data)
static int	do_reload (int loading)
static char *	handle_cli_refresh (struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
static char *	handle_cli_reload (struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
static char *	handle_cli_status (struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
static int	refresh_list (const void *data)
Variables
static struct ast_cli_entry	cli_refresh = AST_CLI_DEFINE(handle_cli_refresh, "Performs an immediate refresh")
static struct ast_cli_entry	cli_reload = AST_CLI_DEFINE(handle_cli_reload, "Reloads the DNS manager configuration")
static struct ast_cli_entry	cli_status = AST_CLI_DEFINE(handle_cli_status, "Display the DNS manager status")
static int	enabled
static struct refresh_info	master_refresh_info
static int	refresh_interval
static int	refresh_sched = -1
static pthread_t	refresh_thread = AST_PTHREADT_NULL
static struct sched_context *	sched

---

Detailed Description

Background DNS update manager.

Author:

Kevin P. Fleming <kpfleming@digium.com>

Bug:

There is a minor race condition. In the event that an IP address of a dnsmgr managed host changes, there is the potential for the consumer of that address to access the in_addr data at the same time that the dnsmgr thread is in the middle of updating it to the new address.

Definition in file dnsmgr.c.

---

Define Documentation

#define REFRESH_DEFAULT   300

Definition at line 71 of file dnsmgr.c.

Referenced by do_reload().

---

Function Documentation

int ast_dnsmgr_changed

(

struct ast_dnsmgr_entry *

entry

)

Check is see if a dnsmgr entry has changed.

Return values:

	non-zero	if the dnsmgr entry has changed since the last call to this function
	zero	if the dnsmgr entry has not changed since the last call to this function

Definition at line 191 of file dnsmgr.c.

References ast_mutex_lock(), ast_mutex_unlock(), ast_dnsmgr_entry::changed, and ast_dnsmgr_entry::lock.

Referenced by iax2_do_register().

{
   int changed;

   ast_mutex_lock(&entry->lock);

   changed = entry->changed;
   entry->changed = 0;

   ast_mutex_unlock(&entry->lock);
   
   return changed;
}

struct ast_dnsmgr_entry* ast_dnsmgr_get	(	const char *	name,
		struct sockaddr_in *	result,
		const char *	service
	)			[read]

Allocate a new DNS manager entry.

Parameters:

	name	the hostname
	result	where the DNS manager should store the IP address as it refreshes it. it.

This function allocates a new DNS manager entry object, and fills it with the provided hostname and IP address. This function does not force an initial lookup of the IP address. So, generally, this should be used when the initial address is already known.

Returns:

a DNS manager entry

Version:

1.6.1 result changed from struct in_addr to struct sockaddr_in to store port number

Definition at line 88 of file dnsmgr.c.

References ast_calloc, ast_mutex_init(), AST_RWLIST_INSERT_HEAD, AST_RWLIST_UNLOCK, AST_RWLIST_WRLOCK, ast_strlen_zero(), ast_dnsmgr_entry::last, ast_dnsmgr_entry::lock, ast_dnsmgr_entry::result, and ast_dnsmgr_entry::service.

Referenced by ast_dnsmgr_lookup().

{
   struct ast_dnsmgr_entry *entry;
   int total_size = sizeof(*entry) + strlen(name) + (service ? strlen(service) + 1 : 0);

   if (!result || ast_strlen_zero(name) || !(entry = ast_calloc(1, total_size)))
      return NULL;

   entry->result = result;
   ast_mutex_init(&entry->lock);
   strcpy(entry->name, name);
   memcpy(&entry->last, result, sizeof(entry->last));
   if (service) {
      entry->service = ((char *) entry) + sizeof(*entry) + strlen(name);
      strcpy(entry->service, service);
   }

   AST_RWLIST_WRLOCK(&entry_list);
   AST_RWLIST_INSERT_HEAD(&entry_list, entry, list);
   AST_RWLIST_UNLOCK(&entry_list);

   return entry;
}

int ast_dnsmgr_lookup	(	const char *	name,
		struct sockaddr_in *	result,
		struct ast_dnsmgr_entry **	dnsmgr,
		const char *	service
	)

Allocate and initialize a DNS manager entry.

Parameters:

	name	the hostname
	result	where to store the IP address as the DNS manager refreshes it
	dnsmgr	Where to store the allocate DNS manager entry

This function allocates a new DNS manager entry object, and fills it with the provided hostname and IP address. This function _does_ force an initial lookup, so it may block for some period of time.

Return values:

	0	success
	non-zero	failure

Version:

1.6.1 result changed from struct in_addr to struct aockaddr_in to store port number

Definition at line 126 of file dnsmgr.c.

References ast_dnsmgr_get(), ast_get_ip_or_srv(), ast_strlen_zero(), ast_verb, and enabled.

Referenced by build_peer(), iax2_append_register(), and transmit_register().

{
   if (ast_strlen_zero(name) || !result || !dnsmgr)
      return -1;

   if (*dnsmgr && !strcasecmp((*dnsmgr)->name, name))
      return 0;

   /* if it's actually an IP address and not a name,
      there's no need for a managed lookup */
   if (inet_aton(name, &result->sin_addr))
      return 0;

   ast_verb(4, "doing dnsmgr_lookup for '%s'\n", name);

   /* do a lookup now but add a manager so it will automagically get updated in the background */
   ast_get_ip_or_srv(result, name, service);
   
   /* if dnsmgr is not enable don't bother adding an entry */
   if (!enabled)
      return 0;
   
   ast_verb(3, "adding dns manager for '%s'\n", name);
   *dnsmgr = ast_dnsmgr_get(name, result, service);
   return !*dnsmgr;
}

int ast_dnsmgr_refresh

(

struct ast_dnsmgr_entry *

entry

)

Force a refresh of a dnsmgr entry.

Return values:

	non-zero	if the result is different than the previous result
	zero	if the result is the same as the previous result

Definition at line 183 of file dnsmgr.c.

References dnsmgr_refresh().

Referenced by iax2_do_register(), and sip_reg_timeout().

{
   return dnsmgr_refresh(entry, 0);
}

void ast_dnsmgr_release

(

struct ast_dnsmgr_entry *

entry

)

Free a DNS manager entry.

Parameters:

entry

the DNS manager entry to free

Returns:

nothing

Definition at line 112 of file dnsmgr.c.

References ast_free, ast_mutex_destroy(), AST_RWLIST_REMOVE, AST_RWLIST_UNLOCK, AST_RWLIST_WRLOCK, ast_verb, and ast_dnsmgr_entry::lock.

Referenced by delete_users(), peer_destructor(), sip_destroy_peer(), and sip_registry_destroy().

{
   if (!entry)
      return;

   AST_RWLIST_WRLOCK(&entry_list);
   AST_RWLIST_REMOVE(&entry_list, entry, list);
   AST_RWLIST_UNLOCK(&entry_list);
   ast_verb(4, "removing dns manager for '%s'\n", entry->name);

   ast_mutex_destroy(&entry->lock);
   ast_free(entry);
}

AST_MUTEX_DEFINE_STATIC

(

refresh_lock

)

static AST_RWLIST_HEAD_STATIC	(	entry_list	,
		ast_dnsmgr_entry
	)			[static]

int dnsmgr_init

(

void

)

Provided by dnsmgr.c

Definition at line 350 of file dnsmgr.c.

References ast_cli_register(), ast_log(), cli_refresh, cli_reload, cli_status, do_reload(), LOG_ERROR, and sched_context_create().

Referenced by main().

{
   if (!(sched = sched_context_create())) {
      ast_log(LOG_ERROR, "Unable to create schedule context.\n");
      return -1;
   }
   ast_cli_register(&cli_reload);
   ast_cli_register(&cli_status);
   ast_cli_register(&cli_refresh);
   return do_reload(1);
}

static int dnsmgr_refresh	(	struct ast_dnsmgr_entry *	entry,
		int	verbose
	)			[static]

Definition at line 156 of file dnsmgr.c.

References ast_copy_string(), ast_get_ip_or_srv(), ast_inet_ntoa(), ast_log(), ast_mutex_lock(), ast_mutex_unlock(), ast_verb, ast_dnsmgr_entry::changed, inaddrcmp(), ast_dnsmgr_entry::last, ast_dnsmgr_entry::lock, LOG_NOTICE, ast_dnsmgr_entry::result, and ast_dnsmgr_entry::service.

Referenced by ast_dnsmgr_refresh(), and refresh_list().

{
   char iabuf[INET_ADDRSTRLEN];
   char iabuf2[INET_ADDRSTRLEN];
   struct sockaddr_in tmp;
   int changed = 0;
        
   ast_mutex_lock(&entry->lock);
   if (verbose)
      ast_verb(3, "refreshing '%s'\n", entry->name);

   tmp.sin_port = entry->last.sin_port;
   
   if (!ast_get_ip_or_srv(&tmp, entry->name, entry->service) && inaddrcmp(&tmp, &entry->last)) {
      ast_copy_string(iabuf, ast_inet_ntoa(entry->last.sin_addr), sizeof(iabuf));
      ast_copy_string(iabuf2, ast_inet_ntoa(tmp.sin_addr), sizeof(iabuf2));
      ast_log(LOG_NOTICE, "dnssrv: host '%s' changed from %s:%d to %s:%d\n", 
         entry->name, iabuf, ntohs(entry->last.sin_port), iabuf2, ntohs(tmp.sin_port));
      *entry->result = tmp;
      entry->last = tmp;
      changed = entry->changed = 1;
   }

   ast_mutex_unlock(&entry->lock);
   return changed;
}

int dnsmgr_reload

(

void

)

Provided by dnsmgr.c

Definition at line 362 of file dnsmgr.c.

References do_reload().

{
   return do_reload(0);
}

void dnsmgr_start_refresh

(

void

)

Provided by dnsmgr.c

Definition at line 244 of file dnsmgr.c.

References ast_sched_add_variable(), AST_SCHED_DEL, master_refresh_info, and refresh_list().

Referenced by main().

{
   if (refresh_sched > -1) {
      AST_SCHED_DEL(sched, refresh_sched);
      refresh_sched = ast_sched_add_variable(sched, 100, refresh_list, &master_refresh_info, 1);
   }
}

static void* do_refresh

(

void *

data

)

[static]

Definition at line 205 of file dnsmgr.c.

References ast_sched_runq(), and ast_sched_wait().

Referenced by do_reload().

{
   for (;;) {
      pthread_testcancel();
      usleep((ast_sched_wait(sched)*1000));
      pthread_testcancel();
      ast_sched_runq(sched);
   }
   return NULL;
}

static int do_reload

(

int

loading

)

[static]

Definition at line 367 of file dnsmgr.c.

References ast_config_destroy(), ast_config_load2(), ast_log(), ast_mutex_lock(), ast_mutex_unlock(), ast_pthread_create_background, AST_PTHREADT_NULL, ast_sched_add_variable(), AST_SCHED_DEL, ast_true(), ast_variable_retrieve(), config, CONFIG_FLAG_FILEUNCHANGED, CONFIG_STATUS_FILEUNCHANGED, do_refresh(), enabled, EVENT_FLAG_SYSTEM, LOG_ERROR, LOG_NOTICE, LOG_WARNING, manager_event, master_refresh_info, REFRESH_DEFAULT, refresh_interval, and refresh_list().

Referenced by dnsmgr_init(), dnsmgr_reload(), and handle_cli_reload().

{
   struct ast_config *config;
   struct ast_flags config_flags = { loading ? 0 : CONFIG_FLAG_FILEUNCHANGED };
   const char *interval_value;
   const char *enabled_value;
   int interval;
   int was_enabled;
   int res = -1;

   if ((config = ast_config_load2("dnsmgr.conf", "dnsmgr", config_flags)) == CONFIG_STATUS_FILEUNCHANGED)
      return 0;

   /* ensure that no refresh cycles run while the reload is in progress */
   ast_mutex_lock(&refresh_lock);

   /* reset defaults in preparation for reading config file */
   refresh_interval = REFRESH_DEFAULT;
   was_enabled = enabled;
   enabled = 0;

   AST_SCHED_DEL(sched, refresh_sched);

   if (config) {
      if ((enabled_value = ast_variable_retrieve(config, "general", "enable"))) {
         enabled = ast_true(enabled_value);
      }
      if ((interval_value = ast_variable_retrieve(config, "general", "refreshinterval"))) {
         if (sscanf(interval_value, "%30d", &interval) < 1)
            ast_log(LOG_WARNING, "Unable to convert '%s' to a numeric value.\n", interval_value);
         else if (interval < 0)
            ast_log(LOG_WARNING, "Invalid refresh interval '%d' specified, using default\n", interval);
         else
            refresh_interval = interval;
      }
      ast_config_destroy(config);
   }

   if (enabled && refresh_interval)
      ast_log(LOG_NOTICE, "Managed DNS entries will be refreshed every %d seconds.\n", refresh_interval);

   /* if this reload enabled the manager, create the background thread
      if it does not exist */
   if (enabled) {
      if (!was_enabled && (refresh_thread == AST_PTHREADT_NULL)) {
         if (ast_pthread_create_background(&refresh_thread, NULL, do_refresh, NULL) < 0) {
            ast_log(LOG_ERROR, "Unable to start refresh thread.\n");
         }
      }
      /* make a background refresh happen right away */
      refresh_sched = ast_sched_add_variable(sched, 100, refresh_list, &master_refresh_info, 1);
      res = 0;
   }
   /* if this reload disabled the manager and there is a background thread,
      kill it */
   else if (!enabled && was_enabled && (refresh_thread != AST_PTHREADT_NULL)) {
      /* wake up the thread so it will exit */
      pthread_cancel(refresh_thread);
      pthread_kill(refresh_thread, SIGURG);
      pthread_join(refresh_thread, NULL);
      refresh_thread = AST_PTHREADT_NULL;
      res = 0;
   }
   else
      res = 0;

   ast_mutex_unlock(&refresh_lock);
   manager_event(EVENT_FLAG_SYSTEM, "Reload", "Module: DNSmgr\r\nStatus: %s\r/nMessage: DNSmgr reload Requested\r\n", enabled ? "Enabled" : "Disabled");

   return res;
}

static char* handle_cli_refresh	(	struct ast_cli_entry *	e,
		int	cmd,
		struct ast_cli_args *	a
	)			[static]

Definition at line 273 of file dnsmgr.c.

References ast_cli_args::argc, ast_cli_args::argv, ast_cli(), CLI_GENERATE, CLI_INIT, CLI_SHOWUSAGE, CLI_SUCCESS, ast_cli_entry::command, enabled, refresh_info::entries, ast_cli_args::fd, refresh_info::filter, refresh_list(), refresh_info::regex_present, and ast_cli_entry::usage.

{
   struct refresh_info info = {
      .entries = &entry_list,
      .verbose = 1,
   };
   switch (cmd) {
   case CLI_INIT:
      e->command = "dnsmgr refresh";
      e->usage = 
         "Usage: dnsmgr refresh [pattern]\n"
         "       Peforms an immediate refresh of the managed DNS entries.\n"
         "       Optional regular expression pattern is used to filter the entries to refresh.\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;   
   }

   if (!enabled) {
      ast_cli(a->fd, "DNS Manager is disabled.\n");
      return 0;
   }

   if (a->argc > 3) {
      return CLI_SHOWUSAGE;
   }

   if (a->argc == 3) {
      if (regcomp(&info.filter, a->argv[2], REG_EXTENDED | REG_NOSUB)) {
         return CLI_SHOWUSAGE;
      } else {
         info.regex_present = 1;
      }
   }

   refresh_list(&info);

   if (info.regex_present) {
      regfree(&info.filter);
   }

   return CLI_SUCCESS;
}

static char* handle_cli_reload	(	struct ast_cli_entry *	e,
		int	cmd,
		struct ast_cli_args *	a
	)			[static]

Definition at line 254 of file dnsmgr.c.

References ast_cli_args::argc, CLI_GENERATE, CLI_INIT, CLI_SHOWUSAGE, CLI_SUCCESS, ast_cli_entry::command, do_reload(), and ast_cli_entry::usage.

{
   switch (cmd) {
   case CLI_INIT:
      e->command = "dnsmgr reload";
      e->usage = 
         "Usage: dnsmgr reload\n"
         "       Reloads the DNS manager configuration.\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;   
   }
   if (a->argc > 2)
      return CLI_SHOWUSAGE;

   do_reload(0);
   return CLI_SUCCESS;
}

static char* handle_cli_status	(	struct ast_cli_entry *	e,
		int	cmd,
		struct ast_cli_args *	a
	)			[static]

Definition at line 317 of file dnsmgr.c.

References ast_cli_args::argc, ast_cli(), AST_RWLIST_RDLOCK, AST_RWLIST_TRAVERSE, AST_RWLIST_UNLOCK, CLI_GENERATE, CLI_INIT, CLI_SHOWUSAGE, CLI_SUCCESS, ast_cli_entry::command, enabled, ast_cli_args::fd, refresh_interval, and ast_cli_entry::usage.

{
   int count = 0;
   struct ast_dnsmgr_entry *entry;
   switch (cmd) {
   case CLI_INIT:
      e->command = "dnsmgr status";
      e->usage = 
         "Usage: dnsmgr status\n"
         "       Displays the DNS manager status.\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;   
   }

   if (a->argc > 2)
      return CLI_SHOWUSAGE;

   ast_cli(a->fd, "DNS Manager: %s\n", enabled ? "enabled" : "disabled");
   ast_cli(a->fd, "Refresh Interval: %d seconds\n", refresh_interval);
   AST_RWLIST_RDLOCK(&entry_list);
   AST_RWLIST_TRAVERSE(&entry_list, entry, list)
      count++;
   AST_RWLIST_UNLOCK(&entry_list);
   ast_cli(a->fd, "Number of entries: %d\n", count);

   return CLI_SUCCESS;
}

static int refresh_list

(

const void *

data

)

[static]

Definition at line 216 of file dnsmgr.c.

References ast_log(), ast_mutex_trylock(), ast_mutex_unlock(), AST_RWLIST_RDLOCK, AST_RWLIST_TRAVERSE, AST_RWLIST_UNLOCK, ast_verb, dnsmgr_refresh(), refresh_info::entries, refresh_info::filter, LOG_WARNING, refresh_interval, refresh_info::regex_present, and refresh_info::verbose.

Referenced by dnsmgr_start_refresh(), do_reload(), and handle_cli_refresh().

{
   struct refresh_info *info = (struct refresh_info *)data;
   struct ast_dnsmgr_entry *entry;

   /* if a refresh or reload is already in progress, exit now */
   if (ast_mutex_trylock(&refresh_lock)) {
      if (info->verbose)
         ast_log(LOG_WARNING, "DNS Manager refresh already in progress.\n");
      return -1;
   }

   ast_verb(3, "Refreshing DNS lookups.\n");
   AST_RWLIST_RDLOCK(info->entries);
   AST_RWLIST_TRAVERSE(info->entries, entry, list) {
      if (info->regex_present && regexec(&info->filter, entry->name, 0, NULL, 0))
          continue;

      dnsmgr_refresh(entry, info->verbose);
   }
   AST_RWLIST_UNLOCK(info->entries);

   ast_mutex_unlock(&refresh_lock);

   /* automatically reschedule based on the interval */
   return refresh_interval * 1000;
}

---

Variable Documentation

struct ast_cli_entry cli_refresh = AST_CLI_DEFINE(handle_cli_refresh, "Performs an immediate refresh") [static]

Definition at line 347 of file dnsmgr.c.

Referenced by dnsmgr_init().

struct ast_cli_entry cli_reload = AST_CLI_DEFINE(handle_cli_reload, "Reloads the DNS manager configuration") [static]

Definition at line 346 of file dnsmgr.c.

Referenced by dnsmgr_init().

struct ast_cli_entry cli_status = AST_CLI_DEFINE(handle_cli_status, "Display the DNS manager status") [static]

Definition at line 348 of file dnsmgr.c.

Referenced by dnsmgr_init().

int enabled [static]

Definition at line 73 of file dnsmgr.c.

Referenced by ast_dnsmgr_lookup(), do_reload(), handle_cli_refresh(), and handle_cli_status().

struct refresh_info master_refresh_info [static]

Initial value:

 {
   .entries = &entry_list,
   .verbose = 0,
}

Definition at line 83 of file dnsmgr.c.

Referenced by dnsmgr_start_refresh(), and do_reload().

int refresh_interval [static]

Definition at line 74 of file dnsmgr.c.

Referenced by do_reload(), handle_cli_status(), and refresh_list().

int refresh_sched = -1 [static]

Definition at line 49 of file dnsmgr.c.

pthread_t refresh_thread = AST_PTHREADT_NULL [static]

Definition at line 50 of file dnsmgr.c.

struct sched_context* sched [static]

Definition at line 48 of file dnsmgr.c.